Chicago Bears star cornerback Charles "Peanut" Tillman is a force to be reckoned with on the football field. But, when his baby girl, Tiana, was diagnosed with a life-threatening illness in 2008, there wasn't much he and his wife, Jackie, could do to defend their daughter.

Born February 11, 2008, Tiana weighed a healthy 7 pounds, 5 ounces at birth. But, three months later, Tiana's health took a turn for the worse. "She stopped eating, and she was screaming and really acting different," Jackie says. "That is the day that everything kind of went downhill."

Jackie took action to get Tiana the care she needed—Tiana was life-flighted to Children's Memorial Hospital in Chicago. Charles says he got the earth-shattering news while at football practice. "Coach [Lovie] Smith came over to me, and he told me that Tiana was sick, and she was being rushed to the hospital," Charles says.

At the hospital, doctors told Jackie and Charles their 3-month-old might not make it through the night.

Tiana was diagnosed with dilated cardiomyopathy, or an enlarged heart. And, even though her heart was beating 220 times a minute, it wasn't able to pump enough blood through her tiny body.

While in the hospital, Tiana fought for her life. Doctors said Tiana's only hope was a heart transplant, and she'd have to rely on heart and lung machines to keep her alive while they waited for a donor. Charles and Jackie put Tiana on the donor waiting list, but they knew it would take a miracle to save her. "You think about what you [would] do if she was no longer here; you think about how lonely you'd be, how empty you'd be," Charles says. "Then you just pray."

Three months passed, and Tiana's health was getting worse. Doctors suggested an experimental device called the Berlin heart, and the Tillmans agreed to try it. After an eight-hour surgery, the artificial heart beat life into Tiana, but it was only a temporary solution. She desperately needed a new heart.

Meanwhile, 400 miles away in Minnesota, another mother was watching over her dying son, baby Armando.

Armando was born on May 23, 2008, at 8 pounds, 6 ounces, to single mother Magali and big sister Akary. "It was a happy day," Magali says. "Since I had a girl, having a boy [meant] my family was complete."

Two months later, Magali woke up to every parent's worst fear: Her infant son, who had shown no signs of illness, was struggling for breath. "I got to his crib, and he was having a hard time breathing," Magali says. "I started checking on him, and he was really, really cold."

Magali rushed Armando to a nearby hospital. "They took him off my arms, and immediately they started putting oxygen on him. I heard him crying, so I felt like a huge relief in that moment," she says. "And then he stopped."

Armando was airlifted to the Children's of Minnesota for emergency treatment. After five agonizing days in intensive care, doctors told Magali there was no way to save her baby boy.

Although Armando wouldn't survive, doctors told Magali that his heart was still strong and could save another child. They said they knew of a 6-month-old baby girl who was fighting for her life in Chicago. "[I thought,] 'I bet the mom is sitting on a chair next to her daughter, going through almost the same thing I'm going through,'" Magali says. "But the big difference, that her child might have a chance."

Magali made one of the most difficult decisions of her life—she donated her son's heart. This selfless act was the answer to the Tillmans' prayers, but doctors needed to move quickly: They only had six hours to transfer the heart from Minnesota to Chicago and perform the operation.

With severe storms in Chicago, the pilots landed the plane as close as they could to the hospital. Then, police officers escorted the heart the rest of the way. Charles says he had just returned from Bears training camp when Tiana's doctor called with the good news. When Jackie and Charles were unable to find a cab to take them to the hospital, they say they ran a mile on foot to get there as fast as they could. "When I saw the heart coming in, my adrenaline was pumping like I was in the Superbowl because this was going to save my daughter," Charles says.

The Tillmans were ecstatic that their daughter would get a second chance, but the moment was bittersweet. They knew that in order for Tiana to live, another child died. "I thought about the family the whole day," Charles says. "It was a hard day. It was a good day and a bad day all at the same time."

Magali's decision left Jackie nearly speechless. "There are no words that you can say to somebody who gives a gift like that," Jackie says. "For her to say yes and not know us and not know our situation or anything and save my child's life, there's nothing that can describe it."

Two and a half years later, Tiana, almost 3 years old, is happy and healthy. To this day, Charles and Jackie have never met the family who helped save their little girl's life. "They have pretty strict rules as far as you meeting the family and knowing the family," Charles says.

In fact, the first time Charles saw Armando was on a video shown in Oprah's studio, two minutes before walking on stage. "I didn't know [his] age, race; I didn't know whether the donor was black, white, or whether it was a boy or girl—nothing," Charles says.

Little do Charles and Jackie know, Magali and her 10-year-old daughter Akary are here to meet the Tillman family for the first time.

"I can't imagine what it feels like to see life in this baby girl and that life is because of your son's heart," Oprah says to Magali. "Are you glad you made the decision now?"

"Yes, I'm glad," Magali says.

Jackie and Charles say they've been waiting a long time to meet Magali. "In my head, I have written a letter to you over and over and over again," Jackie says. "When I finally put it all in words, there's not enough—there are no words—to thank you. There's nothing I can say to thank you enough and for you to understand what you saying yes did to us that day, because you gave her life."